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High Thermal Conductivity Silicon Nitride Ceramics
Hirao, Kiyoshi,Zhou, You,Hyuga, Hideki,Ohji, Tatsuki,Kusano, Dai The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.4
This paper deals with the recent developments of high thermal conductivity silicon nitride ceramics. First, the factors that reduce the thermal conductivity of silicon nitride are clarified and the potential approaches to realize high thermal conductivity are described. Then, the recent achievements on the silicon nitride fabricated through the reaction bonding and post sintering technique are presented. Because of a smaller amount of impurity oxygen, the obtained thermal conductivity is substantially higher, compared to that of the conventional gas-pressure sintered silicon nitride, while the microstructures and bending strengths are similar to each other between these two samples. Moreover, further improvement of the thermal conductivity is possible by increasing ${\beta}/{\alpha}$ phase ratio of the nitrided sample, resulting in a very high thermal conductivity of 177 W/($m{\cdot}K$) as well as a high fracture toughness of 11.2 $MPa{\cdot}m^{1/2}$.
Hirao Akira,Tsunoda Yuji,Matsuo Akira,Sugiyama Kenji,Watanabe Takumi The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.3
Dendritic hyperbranched poly(methyl methacrylate)s (PMMA)s, whose branched architectures resemble the 'dendron' part(s) of dendrimer, were synthesized by an iterative methodology consisting of two reactions in each iteration process: (a) a coupling reaction of u-functionalized, living, anionic PMMA having two tert-butyldimethylsilyloxymethylphenyl(SMP) groups with benzyl bromide(BnBr)-chain-end-functionalized PMMA, and (b) a transformation reaction of the introduced SMP groups into BnBr functionalities. These two reactions, (a) and (b), were repeated three times to afford a series of dendron-like, hyperbranched (PMMA)s up to third generation. Three dendron-like, hyperbranched (PMMA)s different in branched architecture were also synthesized by the same iterative methodology using a low molecular weight, functionalized 1,1-diphenylalkyl anion prepared from sec-BuLi and 1,1-bis(3-tert-butyldime-thylsilyloxymethylphenyl)ethylene in the reaction step (b) in each iterative process. Furthermore, structurally similar, dendron-like, hyperbranched block copolymers could be successfully synthesized by the iterative methodology using $\alpha$-functionalized, living, anionic poly(2-(perfluorobutyl) ethyl methacrylate) (PRfMA) in addition to $\alpha$-functionalized, living PMMA. Accordingly, the resulting block copolymers were comprised of both PMMA and PRfMA segments with different sequential orders. After the block copolymers were cast into films and annealed, their surface structures were characterized by angle-dependent XPS and contact angle measurements. All three samples showed significant segregation and enrichment of PRfMA segments at the surfaces.
Identification of glyco-biomarker candidates for lung cancer using novel glyco-technologies
Yoshitoshi Hirao,Hideki Matsuzaki,Jun Iwaki,Minako Abe,Akira Togayachi,Atsushi Kuno,Takashi Ohkura,Hiroyuki Kaji,Masaharu Nomura,Masayuki Noguchi,Yuzuru Ikehara,Hisashi Narimatsu 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
Lung cancer is the leading cause of cancer death worldwide. Currently, lung cancer is classified into two major types, small-cell lung cancer carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC), based on the histological appearance. The histological classification has important implications in the clinical practice guideline and the prediction of the patient prognosis. However, conventional serum markers used in clinical tests are insufficient for clinical demands due to the low sensitivity and the low specificity to distinguish them. We have identified a number of glyco-biomarker candidate molecules from lung cancer cell lines using our developed glycoproteomics technologies such as lectin microarray and LC/MS-based protein analysis. On the validation studies, we found out that the selected molecules showed characteristic lectin biding profiles depending on either SCLC or NSCLC. Therefore, combination of these glyco-biomarkers could be expected to improve the diagnostic accuracy for histological classification in lung cancer compared to protein expression alone.
Resonance Frequency Estimation of Time-Series Data by Subspace Method
Tomoko Hirao,Shuichi Adachi 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper studies an estimation problem of a dominant resonance frequency from time-series data. We proposed an estimatio method which incorporates system identification technique into time-series analysis. However, this method has a problem that the estimated resonance frequency is biased. In this paper, a new method which uses subspace method is proposed based on time-series data. The key idea of this method is to use an auto-covariance function of the time-series data instead of impulse response or ordinary input-output data. Hankel matrix of the time-series is consturcted by the auto-convariance function. Then, subspace method is applied to the Hankel matrix, and the resonance frequency can be calculated. Effectiveness of the method is examined through numerical examples.
Kazuki Hirao 대한정신약물학회 2014 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.12 No.3
Objective: The relationship between paranoia symptoms and underlying prefrontal cortex mechanisms among healthy subjectswas analyzed using near-infrared spectroscopy. Methods: Seventy-eight healthy subjects were assessed for paranoia symptoms using the Japanese version of the ParanoiaChecklist. Changes in hemoglobin concentrations were assessed using 2-channel near-infrared spectroscopy on the surfaceof the prefrontal cortex while subjects performed a verbal fluency test. Results: Changes in the concentration of oxygenated hemoglobin in the prefrontal cortex during a verbal fluency test did notcorrelate with the Japanese version of the Paranoia Checklist. Conclusion: Our findings show that the symptoms of paranoia do not negatively affect the prefrontal cortex function amonghealthy subjects.
Sparse Representation Approach to Inverse Halftoning by Means of K-SVD Dictionary
Masahiro Hirao,Toshiaki Aida 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10
We approach to the problem of inverse halftoning within the frameworks of Bayesian inference and compressed sensing, which is one of the most effective signal processing methods through sparse representation. In this paper, we adopt the K-SVD dictionary for the sparse representation of an original image to be inferred, and develop our previous work with the DCT dictionary restricted to a small number of the slowest basis vectors. The K-SVD dictionary is known to have higher efficiency for sparse representation than the DCT one. Therefore, we can expect that it helps us overcome a heavily ill-posed property of the problem. Numerical analysis confirms the effectiveness of our approach with the K-SVD dictionary, and makes clear the difference between the characteristics of the K-SVD dictionary and those of the restricted DCT one.
High Thermal Conductivity Silicon Nitride Ceramics
Kiyoshi Hirao,You Zhou,Hideki Hyuga,Tatsuki Ohji,Dai Kusano 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.4
This paper deals with the recent developments of high thermal conductivity silicon nitride ceramics. First, the factors that reduce the thermal conductivity of silicon nitride are clarified and the potential approaches to realize high thermal conductivity are described. Then, the recent achievements on the silicon nitride fabricated through the reaction bonding and post sintering technique are presented. Because of a smaller amount of impurity oxygen, the obtained thermal conductivity is substantially higher, compared to that of the conventional gas-pressure sintered silicon nitride, while the microstructures and bending strengths are similar to each other between these two samples. Moreover, further improvement of the thermal conductivity is possible by increasing β/α phase ratio of the nitrided sample, resulting in a very high thermal conductivity of 177 W/(m·K) as well as a high fracture toughness of 11.2 MPa· m1/2.